Stands for Before You Follow. Used on Tumblr by the type of people who get called "Tumblrinas" and "Special Snowflakes" unironically by even more pathetic, fedora-toting, anti-SJW types.

Usually read as"don't follow if you are a shitty person or if you disagree with me in any way or think you are the same fictional characters that i think that i am! ask to follow if you are spacegender, goblinkin, or are named Brad!"

if you dont read my byf before following you should kys okay thanks bye!